Aging-Induced Shifts From a Reliance on Sensory Input to Muscle Cocontraction During Balanced Standing

Abstract

To cope with the deterioration in their sensory input and processing ability, elderly individuals seemed to have developed a strategy of stiffening and freezing their lower legs during upright standing.

The contribution of postural balance analysis in older adult fallers: A narrative review

“…This review has shown that balance evaluations are very different, both in protocols and in measurement methods, and that direct comparisons among studies and data interpretation are extremely limited. Many experimental protocols indicated that increased postural sway in older adults is well documented and research findings highlighted a correlation between postural sway and increased risk of falling not only on a static board (Baloh et al 1994;Benjuya et al 2004;Billot et al 2010;Fernie et al 1982;Hasselkus & Shambes 1975;Kang et al 2009;Lajoie et al 2002;Lord et al 1994;Maki et al 1994;Melzer et al 2004;Stel et al 2003), but also on an unstable board (Nardone et al 1994;Nardone et al 2000;Woollacott & Shumway-Cook 1990;Wolfson et al 1994;Rogers et al 2001). All Medial lateral sway in both the conditions (eyes open and closed) was found to be a distinguishing variable between older "fallers" and "non-fallers" in both static and dynamic narrow stance condition .…”

Normal aging reduces motor synergies in manual pointing

“…A direct comparison to the present study is not possible as these studies did not formally analyze motor equivalence, but their results point in the same direction. For instance, elevated levels of muscular cocontraction were observed in older relative to younger adults (Benjuya et al, 2004), which was interpreted as a strategy of stiffening/freezing the lower extremities. Moreover, older adults were found to differ from younger adults in intersegmental coordination as assessed by accelerometers along the central body axis (Accornero et al, 1997), with older adults tending to sway in an "en bloc" pattern.…”

Stepping over obstacles: Attention demands and aging

“…One interpretation of this is that increased cognitive activity improves postural control as it removes overt attention from an 'overly automised' postural activity [4]. A contrasting suggestion is that a dual-task reduction in postural sway could be due to individuals co-contracting the muscles supporting the ankles [10,11], serving to stiffen the lower limbs. A reduction in sway may therefore be a posture-protective mechanism in response to competing demands on attention resources, which is more likely to be exhibited by older adults who are experiencing greater attentional conflict than younger adults.…”

“…reduced velocity, shorter stride length) [9]. In upright standing it can be difficult to interpret dual-task effects because concurrent cognitive activity has been shown to both increase and decrease postural sway [10,11]. Few studies have examined the effect of concurrent cognitive activity or ageing on foot placement when negotiating obstacles [12][13][14].…”